In a vertical blind disclosed in U.S. Pat. No. 4,844,139, to effect traverse of louvers along a guide member, each louver is first rotated to a neutral position almost perpendicular to the guide member. Another vertical blind proposed in U.S. Pat. No. 4,896,713 can be operated with an electromotive motor or can be remote controlled.
In the motor-driven vertical blind, it is necessary to detect whether or not the louver is in the neutral position, such that the louver is prevented from traversing when the louver is not in the neutral position. For example, in a detection mechanism shown in FIG. 13, a drive shaft 101 of a pulley with a louver operating loop wound around is provided with a projection 103. When limit switches 105 and 107 provided at opposite sides of the drive shaft 101 contact the projection 103, a 0 degree position and a 180 degree position, at which the louver is closed, can be detected, respectively. In such vertical blind, the drive shaft 101 is first rotated to the position where the limit switch 105 or 107 turns on, and is then rotated in reverse by 90 degrees, thereby rotating the louver to the neutral position before transversely moving the louver.
In the conventional vertical blind, at least two limit switches are required for detecting that the louver is in the neutral position, disadvantageously increasing the number of components.
Even though the louver is rotatable between the 0 degree position and the 180 degree position, the limit switches 105 and 107 prevent the drive shaft 101 from completing additional rotational movement. Therefore, the rotation ratio of the pulley must be carefully designed to vary with the loop operation amount necessary for rotating the louver 180 degrees. The conventional vertical blind lacks versatility.
Furthermore, when the louver is between the 0 degree position and the 180 degree position, it cannot be detected instantly whether or not the louver is in the neutral position. By rotating the louver to the 0 or 180 degree position, the 0 or 180 degree position must be once detected, and then the louver must be rotated from the detected position in reverse by 90 degrees. Such operation of the louver is laborious.